Bella Swan is a very likely character. Since she has such a strong connection to Forks, which is her home in the Twilight world. Her journey home could be filled with thoughts of Edward and the vampires she has come to know.
Perhaps it's about one of the werewolves going back to their reservation. They might be reflecting on how their life has changed since the appearance of the vampires in the area. For example, Jacob could be on a trip home and thinking about his complex relationship with Bella and his pack.
An old werewolf who has decided to retire from the pack life and goes on a trip to all the places that were important to the werewolves in the Twilight story. Along the way, they might run into some vampires and have to face old prejudices and form new alliances.
Well, they could go on a trip around the world to gather ancient artifacts that have the power to either strengthen or destroy the vampire - werewolf peace in Forks. This would involve lots of action, mystery, and interactions with different characters from the Twilight world.
In Twilight fanfiction, 'home is wherever you are' likely suggests that the presence of a loved one creates a sense of home no matter the location. It could imply that the emotional bond is stronger than the physical place.
Edward Cullen could be a great main character. Since he is already a part of the Cullen family who loves baseball, he could be the one to hit a crucial home run. Maybe this home run is what saves Bella from some sort of danger during a baseball - related event. For example, the Volturi might be there to cause trouble during a game, and Edward's home run distracts them long enough for Bella to get to safety.
One idea could be a story where a character from 'Twilight' has a hidden talent for baseball and hits a home run that changes the course of the vampire - human relationships in Forks. For example, it might bring the vampires and humans closer together in a unique way, like starting a joint baseball team for the town.
One possible interesting plot could be a character from the Twilight series returning to their hometown and having to face old memories and relationships in a new light. Maybe they discover secrets that were hidden before they left.
Another possibility is that the fanfiction could introduce new characters who play a major role in the 'coming home' story. They could be new vampires or humans who have a connection to the original Twilight characters. For instance, a new vampire who was turned while Bella was away and now she has to deal with this new presence when she comes home, and this new character could bring a whole new set of conflicts and relationships into the story.